I have one of my AD users that keep getting 'Read Only' every time they try and open a file on a network drive. I discovered that in this users security in AD under 'Authenticated Users' the 'Read' box is checked. I am not seeing any other users with this box checked, so I tried unchecking this 'Read' setting and had the user try again. Boom, everything worked great after that. One problem though, the 'Read' check keeps coming back after a short time. I cannot get rid of it.